Free-Space Optical Communications
High-Intensity LED Driver
Current Source and Driver
interfaces
Carrier Generator/Modulator and Sewer-Pipe LED Projector
A switching regulator supplies the current. A power MOSFET switches the LED on and off. LED current can be monitored with a voltmeter (or multimeter set to read volts) connected across the 2-ohm current monitor resistor. Current flow from the current regulator is one-half the instantaneous current flow through the LED, since LED current flows for exactly one-half of the time. The 2-ohm resistor establishes a nominal one-to-one voltage drop to instantaneous laser current relationship. For the Cree XR7090RO, the instantaneous current is set to 500 mA (500 mV).
Construction note: Return grounds directly to LM2675 pin 6
Some Part Numbers
|
The LED Driver Prototype
The LED driver is on the right. The circuit was an afterthought. The LED driver prototype was built on a separate board and mated to the modulator prototype (left) with an interconnecting cable.
